I bought a new bike this weekend:
It's a Dahon Speed P8. As you can see, it's kind of funny-looking. That's because it can fold up in a matter of seconds into a comparatively small package for tucking in the checked luggage on a train, a bus, or (with a case) an airplane. Or bringing into a building with you, or putting in the trunk of a car, etc.
Bikes@Vienna is a cool store across the river in VA that specializes in folders and other non-standard bicycles. I've been thinking about getting a folder for a while, and had been down there last summer to try out various models -- this bike seemed like the right one for me. (A Brompton would be better, but costs twice as much.) They were having a sale this past weekend, so that was as good an excuse as any...I took the Metro out there and rode my new bike back.
It rides pretty well. It also has some nifty features, like a bike pump inside the seat post (you remove the post, pull out the nozzle, and use the seat as the pump handle). But the really cool thing will be the new places it lets me bike, like day trips to Baltimore on the commuter train and weekend trips to Philly, New York, and Boston on Amtrak. Seeing a city by bike is perfect -- you can get around easily, but not so quickly that you miss the city as it passes by.